From 62e02582a41424625d2253b22055ccf36c78e4c6 Mon Sep 17 00:00:00 2001
From: hasufell <hasufell@hasufell.de>
Date: Sun, 1 Jun 2014 16:17:51 +0200
Subject: [PATCH] Make bezier calculation more modular

---
 src/bezier.c | 82 ++++++++++++++++++++++++++++++++++++++++++----------
 src/bezier.h |  1 +
 2 files changed, 67 insertions(+), 16 deletions(-)

diff --git a/src/bezier.c b/src/bezier.c
index edc08b3..7e979a6 100644
--- a/src/bezier.c
+++ b/src/bezier.c
@@ -30,39 +30,89 @@
 #include <stdlib.h>
 
 
+/*
+ * static function declarations
+ */
+static bool get_section_vec(vector *a, vector *b, vector *c, float section);
+
+
+static bool get_section_vec(vector *a, vector *b, vector *c, float section)
+{
+	vector a_tmp,
+		   b_tmp;
+
+	if (!a || !b || !c)
+		return false;
+
+	copy_vector(a, &a_tmp);
+	copy_vector(b, &b_tmp);
+
+	set_null_vector(c);
+
+	SUB_VECTORS(&a_tmp, &b_tmp, c);
+	VECTOR_LEN_SCAL_MUL(c, section, c);
+	ADD_VECTORS(c, b, c);
+
+	return true;
+}
+
+/**
+ * Get the reduced bezier curve which is of one degree less
+ * and strained between the defined sections of the old curve.
+ *
+ * @param bez the bezier curve the calcluate the next from
+ * @param new_bez the new bezier curve, with a newly
+ * allocated vector member [out]
+ * @param section the section which will be applied to all
+ * lines between the bezier vertices
+ * @return true/false for success/failure
+ */
+bool get_reduced_bez_curv(bez_curv *bez, bez_curv *new_bez, float section)
+{
+	vector *vec_arr = malloc(sizeof(*vec_arr) * bez->deg);
+
+	for (uint32_t i = 0; i < bez->deg; i++) {
+		vector new_vec;
+
+		get_section_vec(&(bez->vec[i + 1]),
+				&(bez->vec[i]),
+				&new_vec,
+				section);
+
+		vec_arr[i] = new_vec;
+	}
+
+	new_bez->vec = vec_arr;
+	new_bez->deg = bez->deg - 1;
+
+	return new_bez;
+}
+
 /**
  * Calculate a point on the bezier curve according to the
  * bezier vertices. If section is set to 0.5 then it will
  * return the vector to the point in the middle of the curve.
  *
- * @param obj the object holding the bezier vertices information
+ * @param bez the bezier curve the calcluate the point from
  * @param section the section which will be applied to all
  * lines between the bezier vertices
- * @return the vector to the calculated point
+ * @return the vector to the calculated point, newly allocated
  */
 vector *calculate_bezier_point(bez_curv *bez, float section)
 {
-	vector vec_arr[bez->deg];
-	bez_curv new_bez;
+	bez_curv new_bez = { NULL, 0 };
 
-	for (uint32_t i = 0; i < bez->deg; i++) {
-		vector new_vec;
+	free(new_bez.vec);
 
-		SUB_VECTORS(&(bez->vec[i + 1]), &(bez->vec[i]), &new_vec);
-		VECTOR_LEN_SCAL_MUL(&new_vec, section, &new_vec);
-		ADD_VECTORS(&new_vec, &(bez->vec[i]), &new_vec);
-
-		vec_arr[i] = new_vec;
-	}
-
-	new_bez.vec = vec_arr;
-	new_bez.deg = bez->deg - 1;
+	if (!get_reduced_bez_curv(bez, &new_bez, section))
+		return NULL;
 
 	if (new_bez.deg > 0) {
 		return calculate_bezier_point(&new_bez, section);
 	} else {
 		vector *result_vector = malloc(sizeof(*result_vector));
-		*result_vector = vec_arr[0];
+		*result_vector = new_bez.vec[0];
+
 		return result_vector;
 	}
 }
diff --git a/src/bezier.h b/src/bezier.h
index ccbde1e..04dbafb 100644
--- a/src/bezier.h
+++ b/src/bezier.h
@@ -49,6 +49,7 @@ struct bez_curv {
 };
 
 
+bool get_reduced_bez_curv(bez_curv *bez, bez_curv *new_bez, float section);
 vector *calculate_bezier_point(bez_curv *bez, float section);